/*
 * Copyright 2014 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkCanvasPriv_DEFINED
#define SkCanvasPriv_DEFINED

#include "include/core/SkCanvas.h"
#include "include/core/SkPaint.h"
#include "include/core/SkScalar.h"
#include "include/private/base/SkDebug.h"
#include "include/private/base/SkNoncopyable.h"

#include <cstddef>

class SkDevice;
class SkImageFilter;
class SkMatrix;
class SkReadBuffer;
struct SkRect;
class SkWriteBuffer;

#if defined(GRAPHITE_TEST_UTILS)
namespace skgpu::graphite {
class TextureProxy;
}
#endif

class SkAutoCanvasMatrixPaint : SkNoncopyable {
public:
    SkAutoCanvasMatrixPaint(SkCanvas *, const SkMatrix *, const SkPaint *, const SkRect &bounds);
    ~SkAutoCanvasMatrixPaint();

private:
    SkCanvas *fCanvas;
    int fSaveCount;
};

class SkCanvasPriv {
public:
    // The lattice has pointers directly into the readbuffer
    static bool ReadLattice(SkReadBuffer &, SkCanvas::Lattice *);

    static void WriteLattice(SkWriteBuffer &, const SkCanvas::Lattice &);

    // return the byte-size of the lattice, even if the buffer is null
    // storage must be 4-byte aligned
    static size_t WriteLattice(void *storage, const SkCanvas::Lattice &);

    static int SaveBehind(SkCanvas *canvas, const SkRect *subset)
    {
        return canvas->only_axis_aligned_saveBehind(subset);
    }
    static void DrawBehind(SkCanvas *canvas, const SkPaint &paint)
    {
        canvas->drawClippedToSaveBehind(paint);
    }

    // Exposed for testing on non-Android framework builds
    static void ResetClip(SkCanvas *canvas)
    {
        canvas->internal_private_resetClip();
    }

    static SkDevice *TopDevice(const SkCanvas *canvas)
    {
        return canvas->topDevice();
    }

#if defined(GRAPHITE_TEST_UTILS)
    static skgpu::graphite::TextureProxy *TopDeviceGraphiteTargetProxy(SkCanvas *);
#endif

    // The experimental_DrawEdgeAAImageSet API accepts separate dstClips and preViewMatrices arrays,
    // where entries refer into them, but no explicit size is provided. Given a set of entries,
    // computes the minimum length for these arrays that would provide index access errors.
    static void GetDstClipAndMatrixCounts(const SkCanvas::ImageSetEntry set[], int count, int *totalDstClipCount,
        int *totalMatrixCount);

    static SkCanvas::SaveLayerRec ScaledBackdropLayer(const SkRect *bounds, const SkPaint *paint,
        const SkImageFilter *backdrop, SkScalar backdropScale, SkCanvas::SaveLayerFlags saveLayerFlags,
        SkCanvas::FilterSpan filters = {})
    {
        return SkCanvas::SaveLayerRec(bounds, paint, backdrop, backdropScale, saveLayerFlags, filters);
    }

    static SkScalar GetBackdropScaleFactor(const SkCanvas::SaveLayerRec &rec)
    {
        return rec.fExperimentalBackdropScale;
    }

    static void SetBackdropScaleFactor(SkCanvas::SaveLayerRec *rec, SkScalar scale)
    {
        rec->fExperimentalBackdropScale = scale;
    }

    // Attempts to convert an image filter to its equivalent color filter, which if possible,
    // modifies the paint to compose the image filter's color filter into the paint's color filter
    // slot.
    // Returns true if the paint has been modified.
    // Requires the paint to have an image filter and the copy-on-write be initialized.
    static bool ImageToColorFilter(SkPaint *);
};

/* *
 * This constant is trying to balance the speed of ref'ing a subpicture into a parent picture,
 * against the playback cost of recursing into the subpicture to get at its actual ops.
 *
 * For now we pick a conservatively small value, though measurement (and other heuristics like
 * the type of ops contained) may justify changing this value.
 */
constexpr int kMaxPictureOpsToUnrollInsteadOfRef = 1;

/* *
 * We implement ImageFilters and MaskFilters for a given draw by creating a layer, then applying
 * the filter to the pixels of that layer (its backing surface/image), and then we call restore()
 * to blend that layer to the main canvas.
 *
 * If the paint has neither an image filter nor a mask filter, there will be no layer and paint()
 * returns the original without modification.
 *
 * NOTE: This works by assuming all sources of color and shading are represented by the SkPaint.
 * Operations like drawImageRect must convert to an equivalent drawRect call if there's a mask
 * filter, or otherwise ensure there are no mask filters (e.g. drawAtlas).
 */
class AutoLayerForImageFilter {
public:
    // `rawBounds` is the original bounds of the primitive about to be drawn, unmodified by the
    // paint. It's used to determine the size of the offscreen layer for filters.
    // If null, the clip will be used instead.
    //
    // If `skipMaskFilterLayer` is true, any SkMaskFilter on `paint` will be left as-is and is
    // assumed to be handled by the SkDevice that handles the draw.
    //
    // Draw functions should use layer->paint() instead of the passed-in paint.
    AutoLayerForImageFilter(SkCanvas *canvas, const SkPaint &paint, const SkRect *rawBounds, bool skipMaskFilterLayer);

    AutoLayerForImageFilter(const AutoLayerForImageFilter &) = delete;
    AutoLayerForImageFilter &operator = (const AutoLayerForImageFilter &) = delete;
    AutoLayerForImageFilter(AutoLayerForImageFilter &&) = default;
    AutoLayerForImageFilter &operator = (AutoLayerForImageFilter &&) = default;

    ~AutoLayerForImageFilter();

    const SkPaint &paint() const
    {
        return fPaint;
    }

private:
    void addImageFilterLayer(const SkRect *drawBounds);
    void addMaskFilterLayer(const SkRect *drawBounds);

    void addLayer(const SkPaint &restorePaint, const SkRect *drawBounds, bool coverageOnly);

    SkPaint fPaint;
    SkCanvas *fCanvas;
    int fTempLayersForFilters;

    SkDEBUGCODE(int fSaveCount;)
};

#endif
